It is almost always good to keep your nose below his in the early stage
Just noticed that this really needs to be explained.
One of the most common scenarios is when two aircraft are flying towards each other at the start of an engagement. The aircraft close the range with high aspect and approach the merge head on. When one player is intent on taking a pre merge shot he will fly directly at you trying to reduce any flight patch separation in order to make his shot as easy as possible.
However, it turns out that this is absolutely not the best way to merge. The best way to merge is also the best way to avoid the HO. It is simply to create flight path separation. Of course that might not be easy because anyone intent on a head on shot will try to take away any flight path separation you try to create, he still wants that easy shot.
So, why is creating flight path separation the best thing to do and how does it avoid the head on shot?
Flight path separation is essential for a lead turn, and a lead turn has the potential to give you the largest and fastest advantage possible of any maneuver in air combat executed right from the merge. The amount of flight path separation needed is twice your turn radius at the speed of the merge. A little practice executing lead turns and you will soon find what the looks like. The flight path separation can be achieved above, below or to the left or right of the enemy aircraft but if you are also trying to avoid a head on shot one direction is best. It is what ever direction you need to go to position your below the bandits nose, because that makes it more difficult for the bandit to maintain visual contact and easier for you and it makes it harder for him to take a shot if he attempt to push his nose over. What is more likely is that he will roll to to maintain sight and allow some separation in the hope of snatching it back at the last moment to get the shot. If he does roll, you adjust to stay below his nose and you have to force the flight path separation aggressively, that forces them to keep adjusting all the way in. That explains the quote about keeping your nose below his.
Now, you will almost never get the separation you need for a classic lead turn, but every bit of separation you get will win you some angular advantage if you initiate the turn at the right moment. The trick here is to watch the changing line of sight rate. Simply put, that means how quickly the bandit is moving across your canopy. The correct time to execute the turn is the moment you notice the line of sight rate increase and that always happens in the forward quarter well before the merge, you always turn early. The secret to success is to begin your turn before he begins his. That will maximise the angular advantage you get from this.
So, if you begin to turn into the bandit won't he just get the head on shot he wanted?
No, for three reasons, first you were creating your fight path separation under his nose making it hard for him to maintain visual on you, but making it very easy for you to maintain visual on him. Secondly when you do it correctly, no matter how hard you both pull into each other your noses will never meet, if they do, you messed it up. Thirdly, the final trick up your sleeve is that you not only forced flight path separation, and began your turn early, you now also pull out of plane in the turn, that means that you keep your turn circle tilted relative to theirs. That makes a head on shot very difficult and almost impossible. Even the best head on shooters in the game, and there have been some very good ones, can't get make that shot when you execute it properly.
So, you just avoided the HO, big deal?
It is a big deal because you didn't just avoid the HO, you did it with flight path separation, turning early and out of plane, all the ingredients for optimal angular and positional advantage, it simply doesn't get any better. Best case, a decisive advantage. Worst case, you avoided the HO with minimal advantage and the fight goes on. Where you end up between those two extremes only depends on how well you do it.
It's a bit more difficult and a bit more scary against the heavily armed high speed fighters, which is why that type of aircraft is the first choice for those who rely heavily on high aspect shots.
However, the method I described still works very well when you learn how to do it regardless of the type of fighter you are engaging so it should be what you do at the beginning of every single 1v1 engagement. Obviously, for anything more than 1v1, or against bombers different tactics may be more appropriate.
Hope that helps.
Badboy